Tunable transportable spectroradiometer based on an acousto-optical tunable filter: Development and optical...

Area of Science:

• Optical Engineering
• Metrology
• Spectroscopy

Background:

• Accurate thermodynamic temperature determination is crucial for scientific and industrial applications.
• Existing spectroradiometers face challenges with stray light and precise wavelength control.
• Black body temperature measurements above the silver freezing point require specialized instrumentation.

Purpose of the Study:

• To develop a high-performance, transportable spectroradiometer for precise thermodynamic temperature metrology.
• To enable accurate non-contact thermometry for materials with varying emissivity.
• To overcome limitations of existing instruments regarding stray light and wavelength stability.

Main Methods:

• Utilized an acousto-optical tunable filter (AOTF) for rapid and continuous wavelength tuning (650 nm-1000 nm).
• Implemented a double-pass configuration to effectively attenuate diffraction side lobes and stray light.
• Calibrated instrument tunability using an Argon spectral lamp and characterized spectral responsivity via two complementary methods.

Main Results:

• Achieved high relative signal stability (few 10⁻⁴) and excellent wavelength stability (1 pm) over several hours.
• Demonstrated reproducible wavelength calibration within 10 pm over one week.
• Validated the instrument's capability for thermodynamic temperature determination and multispectral thermometry.

Conclusions:

• The developed AOTF-based spectroradiometer is a versatile and high-performance instrument for precise temperature metrology.
• Its design effectively minimizes stray light, enhancing measurement accuracy.
• The instrument is suitable for both fundamental thermodynamic temperature research and industrial non-contact thermometry.